The present invention relates generally to the interferometric arts, and more particularly pertains to interferometers which are useful for either adding or subtracting image detail in first and second images.
Image subtraction is useful to detect differences between images, and may be used in military applications and such commercial fields as urban development, highway planning, land use, new construction, and earth resources studies. Image subtraction might also find use in image communications as a means of bandwidth compression since it would be necessary to transmit only the differences between images in successive cycles rather than the entire image in each cycle.
The following methods of image subtraction and their advantages/disadvantages were investigated by the inventors.
I. Interferometric (Additive Subtraction) Methods
A. grating Shearing Method PA1 B. holographic Methods PA1 A. ronchi Grating Coding PA1 C. diffuser Coding PA1 A. r. shulman, Proc. IXth ICO-CIO Conference (Santa Monica, Calif.) Oct. 9-13, 1972, pp. 523-525. PA1 J. w. goodman, Introduction to Fourier Optics (McGraw-Hill, New York, 1968), pp. 150-154.
S. h. lee, S. K. Yao, and A. G. Milnes, J. Opt. Soc. Am. 60, 1037 (1970). PA2 S. k. yao and S. H. Lee, Appl. Opt. 10, 1154 (1971). PA2 L. s. watkins, Appl. Opt. 12, 1880 (1973). PA2 1. Gabor and Stroke Method PA2 2. Bromley and Thompson Method PA2 1. K. S. Pennington, P. M. Will, and G. L. Shelton, Opt. Commun. 4, 113 (1970). PA2 2. S. R. Dashiell, A. W. Lohman, and J. D. Michaelson, Opt. Commun. 8, 105 (1973). PA2 Y. belveaux and S. Lowenthal, Proc. IXth ICO-CIO Conference (Santa Monica, Calif.), Oct. 9-13, 1972 p. 221. PA2 S. debrus, M. Francon, and C. P. Grover, Opt. Commun. 4, 172 (1971). PA2 S. debrus et al., Opt. Commun. 6, 15 (1972). PA2 S. debrus et al., Proc. IXth ICO-CIO Conference (Santa Monica, Calif.) Oct. 9-13, 1972, p. 152.
D. gabor, G. W. Stroke, R. Restrick, A. Funkhouser, and D. Brumm, Phys. Lett. 18, 116 (1965). PA3 G. w. stroke, An Introduction to Coherent Optics and Holography (academic, New York, 1969, pp. 90-96. PA3 A. r. shulman, Optical Data Processing (Wiley, New York, 1970), pp. 525-530. PA3 K. bromley, M. A. Monahan, J. F. Bryant, and B. J. Thompson, Appl. Phys. Lett. 14, 67 (1969). PA3 K. bromley et al., Appl. Opt. 10, 174 (1971).
II. Coding Methods
B. Polarization Interference Fringe Coding
III. Positive-Negative Superposition (Multiplicative Subtraction) Method
Table 1 summarizes some characteristics of each of the different approaches.
From the table it may be seen that the grating-shearing method (I-A) is the simplest and quickest of the optical approaches, requiring only one step (the final optical processing stage) beyond the recording and developing of the two input photographs to be subtracted.